Brakes not holding at staging light

I am sure this issue is on here, but after searching for the past hour I can't find the answers I am looking for, so you have to forgive me if this is a common issue/ topic.
Anyway, car facts: 98 Trans Am with slotted rotors, hawk pads, stock calipers, 3400 stall, MT Drag radials. My brakes are not holding at the staging light when I load the car, so I don't load the stall as much, so I don't roll, etc.
After bleeding the brakes a few times, my braking issue still persists. I can't see it being a brake caliper issue as all four are fine. I unhooked the ABS and the issue still happened. I am starting to think I may have a brake master cylinder issue, but I am not sure.
Any thoughts would be appreciated.
Thanks